Climate change threatens genetic diversity, future of world’s caribou

Caribou in southern and eastern Canada may disappear from most of their current range in 60 years if climate change takes the toll on their habitat that scientists are predicting.

In order to reach that conclusion, scientists looked at genetic diversity in caribou and whether that diversity was linked to stable habitats. They found that caribou populations in the most climatically stable areas had the greatest genetic diversity, which is important because genetically diverse populations are more able to adapt to change. The scientists note that future climate forecasts bode ill for both caribou habitat and their genes. The results of their research are published in the Dec. 15 online edition of in the journal Nature Climate Change

“Caribou can respond to habitat change in three ways:,” said Kris Hundertmark, co-author and wildlife biologist-geneticist at the University of Alaska Fairbanks Institute of Arctic Biology. “They can move to new suitable habitat, adapt to the changed habitat or die.”

Caribou populations are predicted to become more isolated and fragmented as climate change shrinks their habitat and they have fewer opportunities for genes to flow between individuals and herds, explained Hundertmark.

“When a population loses genetic diversity, they lose the ability to adapt to change,” Hundertmark said, adding that although Alaska herds are expected to fare slightly better than other populations at least in the near future, they are still facing significant challenges.

“Climate change in Alaska means we’re going to see more fires and, while that’s good for moose, it’s really bad for caribou,” Hundertmark said. “It’s going to burn lichen beds that can take at least 50 years to recover and reduce viable caribou habitat.”

Hundertmark and then-graduate student Karen Mager, who collected 655 tissues samples from 20 of Alaska’s 32 herds, developed genetic profiles of Alaska’s caribou. The two credit a successful collaboration with state and federal fish and game biologists and hunters over several years with making sample collection possible.

The scientists, part of a team headed by researchers at Laval University in Quebec, used climate reconstructions from 21,000 years ago to the present to predict where caribou habitat would likely exist. They matched populations with high genetic diversity to areas with the most stable habitat over time.

Bolstered by the success of their retrospective analysis, the scientists forecasted caribou habitat to the year 2080 using a ‘business-as-usual’ climate model: the Intergovernmental Panel on Climate Change’s A1B model. The outcome is grim.

“Those caribou herds that shift their range to remain within their habitat and those herds that are reduced in size and become isolated from neighboring herds are those most threatened with loss of genetic diversity,” said Hundertmark. “That is why it is important to know what areas will be have the most habitat stability in the future.”

The team predicts that viable caribou habitat will shift north, the southernmost herds will disappear and herds in northeastern North America will become more threatened with extinction, losing up to 89 percent of their current habitat.

Caribou in western North America will also be affected, although to a lesser extent, and have a better chance of retaining what remains of genetic diversity and therefore adaptability to change.

“This study gives us strong evidence from a widespread species that the stability of the climate makes a difference in the amount of genetic diversity retained within a species,” said Mager.

ADDITIONAL INFORMATION: The paper, “Genetic Diversity in Caribou Linked to Past and Future Climate Change,” is published at Nature Climate Change online, http://www.nature.com/nclimate/index.html. Journalists who don’t have access to the full paper can contact Hundertmark for a copy.